This invention lies in the field of improved apparatus and processes for making hollow plastic articles, particularly multilayered plastic articles, such as containers.
Many processes have been advanced for manufacturing hollow plastic articles and some of these processes offer the possibility of making articles formed of a plurality of layers wherein an inner wall can be formed of a plastic material having certain desired properties and also with an outer wall of a plastic material exhibiting other desired properties. For example, Berger U.S. Pat. No. 3,122,598 discloses a process for forming decorative plastic articles using injection molding techniques, Sherman U.S. Pat. No. 2,710,987 discloses a method and apparatus for forming laminated plastic articles using extrusion blow-molding techniques, and Valyi U.S. Pat. No. 3,719,735 discloses a technique for injection blow-molding a multilayered container from a composite parison which is itself formed by injecting a thermoplastic material over a preformed liner.
Previously, I have discovered apparatus and technique for forming multi-walled containers using a preformed thermoplastic sheet member having deposited and shaped thereon a quantity of thermoplastic material. Such preform structure is then thermoformed and blow-molded (see my co-pending application Ser. No. 820,444 filed Aug. 1, 1977 now abandoned).
In order to provide a thermoforming stretch blow-molding technique which can be practiced to produce a container without the necessity for lip formation in a preform and which can be practiced so as to trim during manufacture excess material away from the rim portion thereof, an advance in the new thermoform-stretch-blow molding art is needed.